Ignition plug

The spark plug design addresses bondability and manufacturability issues by maintaining a specific unmelted area ratio (Su/Sc) and molten depth (Lmin/L) ratio, ensuring stable joint formation and performance even with larger tip sizes.

JP2025121568APending Publication Date: 2025-08-20DENSO CORP
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Patent Information

Application Number
JP2024017057
Authority / Receiving Office
JP · JP
Patent Type
Applications
Current Assignee / Owner
Filing Date
2024-02-07
Publication Date
2025-08-20

AI Technical Summary

Technical Problem

Conventional spark plug manufacturing methods face challenges in ensuring bondability and manufacturability when larger tip sizes are required, leading to issues like spatter formation and difficulty in maintaining a predetermined discharge gap due to increased thermal stress.

Method used

A spark plug design with a cylindrical tip welded to the ground electrode, where a specific ratio of unmelted area to total area (Su/Sc) and minimum molten depth (Lmin/L) is maintained to ensure a stable joint, reducing energy requirements and suppressing spatter and crack formation.

Benefits of technology

The design achieves stable tip bondability and quality even with larger tip sizes, suppressing spatter and crack formation, thereby ensuring consistent performance under thermal stress.

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Abstract

To provide an ignition plug capable of realizing a required quality with a good manufacturability while ensuring a chip bondability even when a chip size welded to a ground electrode is increased.SOLUTION: An ignition plug 1 includes: a center electrode 3; a ground electrode 4; and a cylindrical tip 5 welded to a front surface 41 of the ground electrode 4 facing the center electrode 3, and has a melted and solidified part 6 serving as a bonded portion formed in contact with an unmelted part 50 of the tip 5. In a cross section along the front surface 41, a ratio Su / Sc of an area Su of the unmelted part 50 of the chip existing inside the melted and solidified part 6 to an area Sc of the chip 5 before welding is in a relationship of the following Expression 1, when a distance between an outer peripheral edge 61 of the melted and solidified part 6 and the unmelted part 5 in a tip radial direction Y is defined as a melting depth, a ratio Lmin / L of a minimum melting depth Lmin to a diameter L of the tip 5 before welding is in a relationship of the following Expression 2. Expression 1: 0.04≤Su / Sc≤0.36, Expression 2: 0.20≤Lmin / L.SELECTED DRAWING: Figure 1
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Citation Information

Patent Citations

  • Method of manufacturing spark plug

    JP2011044440A